Nutrition is a topic that is vitally important, yet it creates a lot of confusion. Even people dedicated to fitness and wellness have widely varying positions on what to eat, when to eat it, and what happens when you do. This is especially prevalent in the gym “community” and all manner of diet programs materialize to point people in certain directions, and perhaps no topic is more frequently debated than post-workout nutrition.
For the evidence-minded, there is some information out there and I captured some of the pertinent stuff here.
On glycogen replenishment
Three sets to failure (using a 12 rep max intensity) produced only a 26% reduction of glycogen stores in the muscle.
Post-training carb ingestion evidence is supported, but only in tests conducted with endurance events like a 2-hour bout of cycling.
Potential exists for the same benefit for multiple sessions of resistance training in the same day, but otherwise the urgency of post-training glycogen is greatly diminished.
Moderate volume/high intensity weight training has been shown to deplete muscle glycogen by only 36-39%.
Even in the event of complete glycogen depletion, a rare event in weight training scenarios, no difference was noted between immediate consumption of high glycemic carb meals and a 2-hour wait to begin consumption. A study which added 165 grams of fat to post-training meals to remove any theoretical benefit of high-glycemic carb ingestion produced no difference in glycogen muscle content 24 hours post training.
On muscle protein breakdown
Research has consistently shown that with elevated plasma amino acids the effect of insulin elevation on net muscle protein balance plateaus at roughly 3-4 times the fasting level. This is easily accomplished with a mixed meal.
A 45-gram dose of whey protein isolate takes 50 minutes to spike blood amino acid levels. Insulin peaked 40 minutes after ingestion & remained elevated to the level needed to maximize net muscle protein balance for 2 hours.
The recommendation for lifters to spike insulin post-exercise is somewhat trivial.
On protein synthesis
Evidence supporting an immediate consumption of post-training protein for maximizing protein synthesis is lacking. One study showed a 3-fold increase in protein synthesis immediately post-exercise vs 12% when delaying consumption, however the exercise was long, moderate aerobic work. Every other study is contradictory and even the ones showing a positive effect on weight-training exercise were conducted on untrained individuals.
Numerous studies have been done using pre and post training supplementation, mostly with untrained and elderly males. Results vary from dramatic increases in lean muscle mass to no significant difference. The one significant study done with well-trained young males, consuming a 42 Gram protein shake (low carb) before and after training resulted in no difference in muscle mass or total body mass after 10 weeks of progressive training using a 4-day split.
Evidence is lacking for the existence of an “anabolic window” of opportunity for nutrient timing around training. In the case of fasted training in the morning, it makes sense to immediately consume a protein supplement after training. This also holds true if it’s been 3-4 hours since the last meal.
In the case of non-fasted training, studies suggest consuming 20 grams of whey protein immediately before training elevates muscle amino acid uptake for up to 3 hours, making post-training protein redundant. No difference is noted whether protein is consumed immediately post-training or 1-2 hours later.
High quality protein at a rate of .18-.23 g per lb of lean body mass pre and post training is a fairly foolproof general guideline for maximizing acute anabolic effects. Additionally, pre and post training meals shouldn’t be separated by more than about 3-4 hours.
Carbohydrate consumption pre and post training is a gray area lacking any cohesive data. For weight training vs. endurance activity, the recommendation to add carbohydrate shows no benefit. Two studies have shown no impact from adding carbohydrate to a casein hydrolysate supplement. In one study, adding 50 grams of maltodextrin to a 25-gram whey supplement post-training did not improve muscle protein balance compared to the whey protein alone.